Expandable vertebral implant

ABSTRACT

An expandable prosthetic implant for engagement between vertebrae includes a first member having a first end, a second end, a plurality of extensions and a hollow interior portion extending from the first end to the second end, wherein the plurality of extensions extend from the first end to the second end. A second member includes a first end, a second end, a hollow interior portion extending from the first end to the second end, and a plurality of extensions extending from the second end to the first end. The plurality extensions of the first member are configured to coaxially interdigitate with the second member, and the plurality of extensions of the second member are configured to coaxially interdigitate with the first member. The first member of the implant is moveable relative to the second member along a longitudinal axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/810,858 filed on Nov. 13, 2017, which is a continuation of U.S.patent application Ser. No. 15/147,363 filed on May 5, 2016, which isincorporated in its entirety herein.

FIELD OF THE INVENTION

The present invention relates to a device to support the spine afterremoval of at least a part of a vertebra. In particular, the device maybe in the form of a multi-level implant which can replace multiplevertebral bodies.

BACKGROUND OF THE INVENTION

When a vertebra is damaged or diseased, surgery may be used to replacethe vertebra or a portion thereof with a prosthetic device to restorespinal column support. For example, vertebral body replacement iscommonly required in the treatment of vertebral fracture, tumor, orinfection.

In recent years, several artificial materials and implants have beendeveloped to replace the vertebral body, such as, for example, titaniumcages, ceramic, ceramic/glass, plastic or PEEK, and carbon fiberspacers. Recently, various expandable prosthetics or expandable cageshave been developed and used for vertebral body replacement. Theexpandable prosthetic devices are generally adjustable to the size ofthe cavity created by a corpectomy procedure and typically are at leastpartially hollow to accommodate bone cement or bone fragments tofacilitate fusion in vivo. Some expandable implants may be adjustedprior to insertion into the cavity, while others may be adjusted insitu. Two advantages of the vertebral body replacement using anexpandable prosthetic device that is adjustable in situ is that it iseasy to place or insert and it permits an optimal, tight fit by in vivoexpansion of the device. Some other advantages offered by an expandableprosthetic device are that they can facilitate distraction across theresected vertebral defect and allow immediate load bearing after acorpectomy procedure.

Instrumentation and specialized tools for insertion of a vertebralimplant is one important design parameter to consider when designing avertebral implant. Spinal surgery procedures can present severalchallenges because of the small clearances around the prosthetic when itis being inserted into position. Another important design considerationincludes the ability of the device to accommodate various surgicalapproaches for insertion of the vertebral implant and considerations inpositioning the device within differing anatomical structures.

SUMMARY OF THE INVENTION

According to one embodiment, an expandable prosthetic implant forengagement between vertebrae includes a first member having a first end,a second end, a plurality of extensions and a hollow interior portionextending from the first end to the second end, wherein the plurality ofextensions extend from the first end to the second end. A second memberincludes a first end, a second end, a hollow interior portion extendingfrom the first end to the second end, and a plurality of extensionsextending from the second end to the first end. The plurality extensionsof the first member are configured to coaxially interdigitate with thesecond member, and the plurality of extensions of the second member areconfigured to coaxially interdigitate with the first member. The firstmember of the implant is moveable relative to the second member along alongitudinal axis.

In one embodiment, a ring is positioned coaxial to the first member andthe second member and axially fixed to the second member. An actuator iscoupled to the second member and operationally coupled to the ring forlocking the first member to the second member.

In one embodiment, at least one of the plurality of extension of thefirst member includes engagement features that engage with thecorresponding engagement element on an inner surface of the ring. In afirst position, the first member is freely moveable in the longitudinalaxis with respect to the second member. When the ring is moved from thefirst position to a second position by rotation of the actuator throughthe use of an instrument, the first member is locked in a position withrespect to the second member.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more readily understood with reference tothe embodiments thereof illustrated in the attached drawing figures, inwhich:

FIG. 1 is a perspective view of an implant in accordance with anembodiment of the present invention;

FIG. 2 is an exploded view of the implant of FIG. 1;

FIG. 3 is a cross-sectional view of the implant of FIG. 1;

FIG. 4 is perspective view of another embodiment of an expandableimplant;

FIG. 5 is an exploded view of implant of FIG. 4;

FIGS. 6A-6D illustrate one embodiment of an endplate used with anexpandable implant;

FIGS. 7A and 7B illustrate cut-out views of the endplate of FIGS. 6A-6Dcoupled to an expandable implant;

FIGS. 8A-8D illustrate another embodiment of an endplate;

FIG. 9 illustrates the endplate of FIGS. 8A-8D coupled to an expandableimplant;

FIG. 10 illustrates the endplate of FIGS. 8A-8D coupled to an instrumentfor positioning the endplate on the expandable implant; and

FIG. 11 illustrates another perspective of the instrument and endplateshown in FIG. 10.

Throughout the drawing figures, it should be understood that likenumerals refer to like features and structures.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the invention will now be described withreference to the attached drawing figures. The following detaileddescription of the invention is not intended to be illustrative of allembodiments. In describing preferred embodiments of the presentinvention, specific terminology is employed for the sake of clarity.However, the invention is not intended to be limited to the specificterminology so selected. It is to be understood that each specificelement includes all technical equivalents that operate in a similarmanner to accomplish a similar purpose. The features of one embodimentmay be employed with other embodiments as the skilled artisan wouldrecognize, even if not explicitly stated herein.

Referring to FIGS. 1-3, a preferred embodiment of an expandablevertebral implant 10 is shown. The implant 10 preferably comprises afirst member 12 which may be operationally coupled with a second member14. The first member 12 and the second member 14 are configured tointerdigitate with one another, and will be discussed in greater detailbelow. To achieve expansion or contraction of the implant 10, adistractor type instrument is used to move the first member 12 withrespect to the second member 14. The implant 10 further comprises a ring16 that is used to lock and unlock the first member 12 with respect tothe second member 14. The first member 12, the second member 14, and thering 16 are preferably centered along a longitudinal axis and define ahollow interior portion which may be filled with bone material, bonegrowth factors, bone morphogenic proteins, or other materials forencouraging bone growth, blood vessel growth or growth of other tissuethrough the many apertures in the device. In one preferred embodiment,members 12, 14, and 16 are made of a polyether ether ketone (PEEK)plastic material. There are several known advantages of PEEK plasticmaterial including being radiolucent, having a mechanical strength thatis close to bone, and may be more easily sterilized than other plastics.In alternate preferred embodiments, the members 12, 14, and 16 may bemade of a biologically inert metal alloys, such as titanium, or othersuitable materials.

Referring to FIGS. 1-3, the first member 12 has a generally cylindricalbody with a distal end 18 and a proximal end 20. In a preferredembodiment, the first member 12 includes a plurality of extensions 22extending form the proximal end 20 to the distal end 18. The pluralityof extensions 22 having an inner surface 24, an outer surface 26, andside surfaces. The plurality of extensions 22 are spaced from oneanother. In one embodiment, the outer surfaces 26 of the plurality ofextensions 22 may have engagement features. The engagement features maybe a plurality of concentric teeth, non-helical threads, ratchet typefeatures, tabs (flexible and non-flexible) and other similar mechanicalelements. On an upper surface at the proximal end 20 of the first member12 in one embodiment there are provided a plurality of endplateengagement features 28. Endplate engagement features 28 are adapted toengage with an endplate. The endplate engagement features 28 as moreclearly illustrated in FIG. 3 may be tabs, fingers, extensions, or inone embodiment arcuate tabs that engage with a corresponding matingfeature of the endplate. As the plurality of extensions 22 are spacedapart from one another, there are a plurality of openings between theplurality of extensions 22.

The second member 14 has a generally cylindrical body with a distal end32 and a proximal end 34. In preferred embodiment, the second member 14includes a plurality of extensions 36 and a plurality of openings 38positioned between the plurality of extensions 44. The plurality ofextensions 36 of the second member includes an inner surface, an outersurface, and side surfaces. The outer surface of the plurality ofextensions 36 include a mating feature 40 configured to be coupled withthe ring 16. It should be noted that the mating feature 40 may be anyfeature that clamps, locks, holds, or secures the ring 16 to the secondmember 14. In one embodiment, the mating feature is a ledge typefeature. The plurality of extensions may also be provided with at leasttwo openings extending from the outer surface to the inner surface ofthe extensions. Pins 42 may be used to lock the ring 16 to the secondmember 14. In the preferred embodiment, the ring 16 is positioned withinthe mating feature 40, and locked to the second member 14 by pins 42.

In a preferred embodiment, at least one of the plurality of extensions44 of the second member 14 includes an opening 45 for receiving anactuator 46 for actuating the ring 16. The extension 44 further includesa slot 47 that extends from the opening 45 towards the distal end 32 ofthe second member 14. In a preferred embodiment, the slot 47 is providedso that the extension 44 may be compressible and/or flexible. In otherembodiments the extension 44 may not be fixed and not compressibleand/or flexible. The opening 45 of the extension 44 may have perimeterthat has a radius or in other embodiments may be linear. In thepreferred embodiment, the internal surfaces of the extension 44 have aradius and are manufacture to be able to receive and secure the actuator46. The internal surfaces of the extension 44 include elements thatallow for the securing the actuator 46, such as tabs, divots,protrusions that correspond to features provided on the actuator 46.

The plurality of extensions of the first member and second member may bedesigned in any geometrical shape for allowing for interdigitating witheither first or second members. For instance, the plurality ofextensions may be in the shape of a cylinder, pyramid, oblong, and othersuitable variation. Preferably, the first member and the second memberconfigured to interdigitate such that one of the first and secondmembers is not received inside the other of the first and secondmembers, for example, in a telescoping fashion. In other words, theouter diameter of both the first and second members may be substantiallyidentical or the same. Although the preferred embodiment illustrates thefirst member and the second member configured to interdigitate, in thealternative, it is envisioned that the first member and the secondmember may be configured to be telescopingly coupled to one another. Forinstance, in some embodiments the first member 12 may be positionedwithin the internal surface of the second member. During operation, aninstrument or any other suitable mechanism may be used to expand thefirst member 12 relative to the second member 14. In other embodiments,the second member may be telescoping relative to the first member 12. Inthese embodiments, the second member 14 is positioned within theinternal surfaces of the first member 12.

The actuator 44 is a cylindrical body having an outer surface and aninner surface. The outer surface of the actuator 44 includes aninstrument engaging surface such a hex shaped groove for receiving acorresponding instrument. Although a hex shaped surface is illustratedin the FIGS. It should be noted that any instrument engaging surfacethat receives a corresponding feature from an instrument may be used tooperate the actuator 46. In the perimeter of the actuator 46 there areprovided rounded teeth for engaging with the actuation features of thering 16. The actuator 46 also includes protrusions that engage with agroove within the inner surfaces of the extension 44. The actuator 46can be rotated within the opening 45, as the protrusions are configuredto move within the groove.

The distal end 32 of the second member 14 also includes endplateengagement features 28. These engagement features 28 are configured tocouple to the second endplate. The endplate engagement features 28 maybe tabs, fingers, extensions, or in one embodiment arcuate tabs thatengage with a corresponding mating feature of an endplate.

The ring 16 is configured to lock the first member 12 to the secondmember 14. The ring 16 has an outer surface 48 and an inner surface 50.The ring 16 also includes a first slot 52 and a second slot 54positioned on opposing sides. On the inner surface 50 of the ring areengagement features 56 that correspond to the engagement features 26 ofthe first member 12. The ring 16 is positioned within the mating feature40 of the second member 14 and locked via pins 42. Pins 42 extend thoughopenings in the extensions of the second member 14 into the first andsecond slots 52, and 54. The ring 16 also includes an upper surface 58and a lower surface 60. The lower surface 60 of the ring has actuationfeatures 62 for allowing the actuation of the ring 16. The actuationfeatures 62 engage with the rounded teeth of the actuator 46. When theactuator is moved, rounded teeth engage with the actuation features 62and causes the ring 16 to be turned. As a result, the engagementfeatures 56 of the ring may align with the engagement features 26 of thefirst member thereby locking the first member 12 to the second member14. In a preferred embodiment, ring 16 is rotated 45 degrees so that theengagement features 56 of the ring 16 engage with the engagementfeatures 26 of the first member 12.

The first member 12 and the second member 14 are configured so that thefirst and second members interdigitate with one another. In thepreferred embodiment, the plurality of extensions 26 of the first member12 are positioned within the plurality of openings 38 in the secondmember. And the plurality of extensions 36 of the second member 14 arepositioned within the plurality of openings 30 in the first member in anunexpanded state. The first member 12 is configured to be engaged withan instrument that translates the first member 12 in the longitudinalaxis, thereby expanding the implant. Once the selected amount ofexpansion is reached, the ring 16 is rotated via the actuator 46 whichlocks the first member 12 relative to the second member 14.

FIGS. 4 and 5 illustrate another embodiment of an expandable implant.FIGS. 4 and 5 illustrate an implant 60 having a first member 62 and asecond member 64. The first and second members 62, 64 are adapted tocorrespondingly mate with one another. The first member 62 includes aplurality of extensions 66 extending from a first end towards a secondend. The second member 64 includes a plurality of extensions 68extending from a first end to a second end. The first and second members62, 64 also include a plurality of openings for receiving the pluralityof extensions 66, 68 thereby interdigitating with one another. At leasttwo of the extensions 66 of the first member include inner side surfaces70 that have engagement features such as ledges, non-helical threads,and/or ratchet style teeth. At least one extension 72 of the secondmember 64 has outer side surfaces 74 that have corresponding engagementfeatures that engage with the engagement features on the side surfacesof the at least two extensions 66 of the first member 62. The extension72 of the second member also includes a slot 76 extending from the firstend towards the second end. The extension 72 of the second member isconfigured to be compressible when an actuator element 78 is rotatedwithin a housing 80.

The actuator 78 is a cylindrical body having an outer surface and aninner surface. The outer surface of the actuator 78 includes aninstrument engaging surface such a hex shaped groove for receiving acorresponding instrument. Although a hex shaped surface is illustratedin the FIGS, it should be noted that any instrument engaging surfacethat receives a corresponding feature from an instrument may be used tooperate the actuator 78. The actuator 78 also includes protrusions thatengage with a groove within the inner surfaces of the extension 72. Theactuator 78 can be rotated within the housing 80, as the protrusions areconfigured to move within the groove. In first position, the firstmember and the second member are not engaged and as a result, the firstmember is moveable with respect to the second member. In a secondposition, the first member is locked to the second member when theactuator is rotated and the protrusion within the groove cause theextension 72 to flex out. When the extension flexes out the sidesurfaces of the legs 82, 84 engage with the engagement features ofextension 70 of the first member.

The benefit provided by the present locking mechanism provided in theabove embodiments is that it allows for a positive lock that engages anddisengages automatically with the engagement and disengagement of thetool with the implant 10, which minimizes the steps the surgeon mustperform during the procedure.

Referring now to FIGS. 6A-6D, in a preferred embodiment, an endplate 80is shown wherein the endplate 80 connects to the first member 12 orsecond member 14 of an expandable implant 10. Although a single endplate80 is illustrated, it should be noted that a second endplate may becoupled to the second member 14 and has similar characteristics of thedescribed endplate 80. In a preferred embodiment, each endplate 80 isgenerally annular in shape when viewed from the end or perpendicular tothe longitudinal axis. It is, however, contemplated that the endplates80 can be other shapes including oblong, elliptical, kidney bean,polygonal, or geometric. Preferably, the endplates 80 may be designed toresemble or mimic the footprint of the vertebral body to which theendplates will engage. In this regard, endplates 80 are configured toengage portions of the vertebrae in a predetermined orientation tomaximize contact of the superior surface of the endplates 80 with bone.

As shown in FIGS. 6B and 6C, in a preferred embodiment, the endplate 80includes an extension 82, and a plurality of slots 84 spaced around theperimeter of the endplate 80. The plurality of slots 84 and an opening86 in the perimeter of the endplate 80 allows the endplate 80 to becompressible. The endplate 80 being compressible facilitates thecoupling of the endplate 80 with either the first member 12 or secondmember 14 of the expandable implant 10. In other embodiments, theendplate 80 may include cutouts 85 for receiving the engagement features28 of the first and second member 12, 14.

In a preferred embodiment, the extension 82 extends from a bottomsurface of the endplate 80 and is configured with rim 88 that extendsaround the perimeter of the extension 82. The extension 82 is alsoconfigured to be mate with the first and second members 12, 14 with akey connection. FIGS. 7A and 7B illustrate the key connection of theendplate 80 with the first member 12 of the expandable implant 10 moreclearly. The rim 88 of the extension 82 is received within the slotportion 66 extending around the perimeter of the first member 12 andsecond member 14. And the ridge portion 64 of the first member 12 isreceived within a slot portion of the extension 82. It should be notedthat the ridge portion 64, the rim 88 and the slot portion may beconfigured in various geometrical shapes to operational mate with theiropposing feature. When positioning the endplate 80, the endplate iscompressed with an instrument and positioned within the hollow portionof the first and/or second member, the endplate 80 is then uncompressedallowing the rim 88 to engage within the slot portion 66 of the firstmember or second member 12, 14.

FIGS. 8A-8D illustrate yet another embodiment of an endplate suitablefor an expandable implant 10. In this embodiment, the endplate 90includes a plurality of slots 92 positioned around the perimeter of theendplate 90. The endplate 90 may also be configured to be in awedge-shaped profile to accommodate the natural curvature of the spine.There is also provided a central hollow cavity that is in fluidcommunication with the hollow cavity of the first member or secondmember of the implant 10. The endplate 90 has an upper surface 94 and alower surface 96, the upper surface 94 is configured to engage with boneand the lower surface 96 is provided with connection elements 98 tocouple with the first or second member 12, 14 of the expandable implant.In some embodiments, the plurality of slots 92 may linear, non-linear,or a combination thereof. In other embodiments the plurality of slots 92may be scalloped, grooved, and/or shaped to efficiently allowcompression and/or expansion of the endplate. In other embodiments, theendplate 90 may be dimensioned to be in other geometrical shapes such asrectangular, octagonal, spherical, elliptical, and any combination thereof. In other embodiments the thickness, width, and length may be variedto provide optimal engagement with the vertebral bodies.

FIG. 9 illustrates the endplate 90 coupled to implant 10. Specifically,endplate 90 is connected to the second member 14 of implant 10. Theconnection elements 98 couple to a ridge portion 100 of the secondmember 14.

FIG. 10 illustrates an instrument 102 coupled to the endplate 90 forpositioning within the implant 10. The instrument 102 is shown asT-handle type device that is capable of connecting to a housing via athreaded connection. The endplate is positioned in the housing 104 toreceive the upper portion of the instrument 102.

FIG. 11 illustrates the instrument 102, endplate 90 and the secondmember 14 in greater detail. The instrument 102 has a threaded portion103 that engages with the threaded portion 105 of the housing 104. Asthe instrument 102 is threaded into the housing 103, the upper portion105 of the instrument 102 contacts the endplate 90 thereby allowing theendplate to expand. Once the endplate 90 is expanded, the endplate 90 isdisengaged from the second member 14. As the instrument 90 is disengagedfrom the endplate 90, the endplate 90 returns to its original position.When the second member 14 is positioned within the housing 104, and theinstrument 12 is disengages from the endplate by unthreading from thehousing, the endplate 90 is coupled to the second member 14 through theconnection element 98. It should be noted that the housing 104 may beany suitable housing that may receive any geometrical shapes of theendplate. It should also be noted that multiple endplates 90 may becoupled to the first and second members or multiple endplates 80 may beused as well as a combination of endplates 80 and 90. In someembodiments a T-handle type instrument may be used, but in otherembodiments any instrument that can apply pressure upon the lowerportion of the endplate to expand the endplate may be used.

The dimensions of endplates 80, 90 can be varied to accommodate apatient's anatomy. In some embodiments, the endplates 80, 90 may haveany shaped including the wedge-shaped profile to accommodate the naturalcurvature of the spine. In anatomical terms, the natural curvature ofthe lumbar spine is referred to as lordosis. When implant 10 is to beused in the lumbar region, the angle formed by the wedge should beapproximately between 3.5 degrees and 16 degrees so that the wedge shapeis a lordotic shape which mimics the anatomy of the lumbar spine. Inalternate embodiments, the wedge shape profile may result from a gradualincrease in height from an anterior side to a posterior side to mimicthe natural curvature, kyphosis, in other regions of the spine. Thus, inother embodiments, the angle may be between about −4 degrees and −16degrees.

Although not shown, in one embodiment, bone engaging members may beadapted to be positioned on the bone engaging surfaces of endplates 80,90. The bone engaging members may comprise conical spikes having acylindrical base portion. In alternate embodiments, differently shapedbone engaging members may be used, or in other embodiments no boneengaging members may be used. The superior or bone engaging surface ofendplate 80 may also include numerous types of texturing to providebetter initial stability and/or grasping contact between the end plateand the respective vertebrae. In a preferred embodiment, the texturingmay be plurality of teeth. In preferred embodiments where the implant 10is manufactured from PEEK or other plastic materials, endplates 80, 90may also include radio-opaque material, such as tantalum markers, whichaid in providing location markers in radiographic images.

In preferred embodiments, the length, diameter, and shape of prostheticdevice 10 may vary to accommodate different applications, differentprocedures, implantation into different regions of the spine, or size ofvertebral body or bodies being replaced or repaired. For example,implant 10 may be expandable to a longer distance to replace multiplevertebral bodies. Also, endplates 80, 90 can be sized and shaped as wellas positioned to accommodate different procedures and approached to thespine. For example, endplates 80, 90 may be made smaller for smallerstatured patients or for smaller regions of the cervical spine. Inaddition, it is not required that endplates 80, 90 be shaped and sizedidentically and in alternate embodiments they can be shaped or sizeddifferently than each other and/or include different bone engagingmembers or texturing.

Depending on the orientation and positioning of the implant 10, theendplates 80, 90 may be provided with a certain degree of lordosis orkyphosis to mimic a natural or unnatural curvature of the spine. Inorder to facilitate the proper alignment of the implant 10, endplates80, 90 may be provided with a first series of markings and endplate 90may be provided with a corresponding second series of markings. When atleast one of the first and second series of markings are aligned, thefirst and second endplates are aligned for a specific approach to thespine (e.g., anterior implantation) and to provide the desired lordosisor kyphosis. The marking scheme (e.g., numbering scheme) aids inassembly of the endplates to the other components of the implant byallowing a user to align the markings for varying approaches to thespine.

The first and second series of markings may include characters,alphanumeric characters, numeric characters, colors, symbols, shapes,words, pictures, or similar indicia. These markings may be etched,engraved, or otherwise marked or applied on the endplates. The firstseries of markings preferably includes a plurality of differentmarkings. In other words, the first series of markings preferablyincludes a plurality of markings that do not repeat and are not thesame.

Similarly, the second series of markings preferably includes a pluralityof different markings which correspond to the first series of markings.When one of the first series of markings is aligned with the one of thesecond series of markings, the endplates are positioned and aligned fora given implantation approach.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations can be made thereto by those skilled in the art withoutdeparting from the scope of the invention as set forth in the claims.

What is claimed is:
 1. A method of stabilizing a spine comprising thesteps of: providing an expandable prosthetic implant for engagementbetween vertebrae, comprising: a first member having a first end, asecond end, a plurality of extensions and and a hollow interior portionextending from the first end to the second end, wherein the plurality ofextensions extend from the first end to the second end, a second memberhaving a first end, a second end, a hollow interior portion extendingfrom the first end to the second end, and a plurality of extensionsextending from the second end to the first end, and wherein the firstmember is moveable relative to the second member along a longitudinalaxis; a ring positioned coaxial to the first member and the secondmember and axially fixed to the second member; and an actuator coupledto the second member and operationally coupled to the ring for lockingthe first member to the second member, wherein the ring is configured tobe rotated from a first position to a second position by rotation of theactuator, and wherein in the first position, the first member is freelymoveable with respect to the second member and in a second position, thefirst member is locked in a position with respect to the second member,positioning the expandable prosthetic implant between vertebrae.
 2. Themethod of claim 1, wherein the first member and the second memberinclude surfaces having a plurality of spaced apart endplate engagementfeatures for coupling to a first and second endplates.
 3. The method ofclaim 1, wherein the second member includes a first opening and a secondopening for a receiving a first pin and a second pin, the first andsecond pin configured to couple the ring to the second member.
 4. Themethod of claim 3, wherein the ring includes a slot extending on theperimeter of outer surface of the ring and configured to receive a firstor second pin.
 5. The method of claim 1, wherein the ring includes aninner surface and an outer surface, the inner surface further includingspaced apart engagement portions for engaging with the engagementfeatures of at least one of the plurality of extensions of the firstmember.
 6. The method of claim 1, wherein the ring includes a marking tovisual gauge the first position and the second position.
 7. The methodof claim 1, wherein the actuator is positioned within one of theplurality of extension of the second member.
 8. The method of claim 1,wherein the plurality of extensions of the second member have an outersurface that includes a ledge that is configured to receive the ring. 9.A method of stabilizing vertebrae comprising: providing an expandableprosthetic implant for engagement between vertebrae, comprising: a firstmember having a first end, a second end, a plurality of extensions andand a hollow interior portion extending from the first end to the secondend, wherein the plurality of extensions extend from the first end tothe second end, a second member having a first end, a second end, ahollow interior portion extending from the first end to the second end,and a plurality of extensions extending from the second end to the firstend, and wherein the first member is moveable relative to the secondmember along a longitudinal axis; and an actuator coupled to one of theplurality of extensions of the second member; wherein at least one ofthe plurality of extension of the first member includes engagementfeatures for couple with the corresponding engagement element configuredon side surfaces of the one of the plurality of extensions of the secondmember, wherein when the actuator is rotated from a first position to asecond position, the one of the plurality of extensions flexes out,whereby the engagement features of the first member engages with theengagement element of the one of the plurality of extensions of thesecond member thereby locking the first member with respect to thesecond member, and wherein in the first position, the first member isfreely moveable with respect to the second member and in a secondposition, the first member is locked in a position with respect to thesecond member, positioning the expandable implant between vertebrae. 10.The method of claim 9, wherein the actuator is positioned within one ofthe plurality of extension of the second member.
 11. The method of claim9, wherein the one of the plurality of extensions of the second memberincludes a housing for receiving the actuator.
 12. The method of claim11, wherein the one of the plurality of extensions includes a slot thatextends from the housing to the second end of the second member.
 13. Themethod of claim 9 wherein the one of the plurality of extensions isconfigured to flex.
 14. The method of claim 9, wherein the engagementfeatures and engagement element are one of non-helical threads, tabs,teeth, and protrusions.
 15. The method of claim 9, wherein an instrumentis used to move the first member relative to the second member.
 16. Themethod of claim 9, wherein the first member and the second memberinclude endplate engagement features for engaging with a first and asecond endplate.